The utility model discloses a pipe joint of an air brake system. The pipe joint comprises a first pipe, a second pipe and a locking member, wherein the first pipe is sleeved with the locking member, and the end part of the first pipe is provided with a limiting surface which can limit the locking member and prevent the locking member dropping from the end part of the first pip; the end part of the second pipe is provided with an external thread, and the locking member is provided with an internal thread matched with the external thread; the end parts of the first and second pipes are provided with sealing surfaces matched with each other, and when the locking member is matched with the second pipe, the two sealing surface can be hermetically matched with each other. When in threaded connection process of the locking member and the second pipe, the two sealing surfaces firstly contact with each other and then gradually generate elastic deformation under the effect of fastening force of the threads, and thereby seal is achieved. The pipe joint achieves direct seal between two pieces of metal without the help of sealing members, is high in seal reliability, and can avoid leakage caused by aging of the sealing members. The utility model also discloses an air brake system.